proof

A set of rules for proving software claims with named checks, especially claims about tests, behavior, edge cases, and completion.

In plain words
What is it for?
It is used to define proof contracts, design behavior tests, review coverage, and report what has or has not been verified.
Why use it?
It prevents an agent from saying that work is complete or correct without identifying evidence that would reveal a false claim.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/kreek/consult/proof
Any agent
npx skills add kreek/consult --skill proof
Clone the repo
git clone --depth 1 https://github.com/kreek/consult

Made for: Claude Code, Codex.

Per session 21 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,783 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00021 $0.02783
Opus 5 $0.00010 $0.01392
Sonnet 5 $0.00004 $0.00557
Haiku 4.5 $0.00002 $0.00278

Measured 2d ago against content hash df5498dbefbb, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

proof scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

agents/.agents/skills/proof/SKILL.md · 223 lines

How it starts

The opening of the file, as written. The whole thing — 223 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Proof

Iron Law

NO ENGINEERING CLAIM WITHOUT A NAMED PROOF.

Prove every non-trivial claim before you call it done. A proof is a named check that would fail if the claim were false: point to that check, or mark the claim unproven. "The tests pass" doesn't count until you can say which test would break if you were wrong.

When to Use

As a completion gate, before any reply that says or implies the work is done, fixed, ready to commit, ready for a PR, or passing:

  • Name the claim and the check that backs it. If there is no check, say what is unproven and which evidence is missing; don't just write unproven and move on.

As the main skill, when the task is the proof itself:

  • Writing or reviewing behavior tests for a feature, bug fix, refactor, flaky test, or any untested behavior.
  • Deciding what needs coverage and which boundary the test should enter through.
  • Turning an agreed spec, domain model, contract, or root-cause finding into Proof Contracts and runnable checks.

When NOT to Use

  • Formatting, typo fixes, or file moves that change no behavior, data, or contract.
  • Mechanical refactors with no behavior surface (renames, file moves, comment-only edits) that tooling or a direct look at the result already confirms. If the refactor changes something a caller can observe, you still need proof.
  • Chasing a bug whose cause you haven't pinned down. Use debugging first; come back once you have a claim to prove.
  • Judging design, complexity, naming, or structure. Use code-review. Reach for proof only when the open question is whether the evidence is enough.
  • Load testing, profiling, or benchmarks. Use performance.
  • Setting up the test runner, linter, or typecheck baseline. Use scaffolding.

Where Proof Enters

Test at boundaries. A boundary is any point where one part of the system hands data to another and the receiver expects a certain shape: between modules, layers, or processes. (This skill also calls these handoffs.) Put the proof where the data's shape, value, state, or error visibly changes. A good boundary test passes against any implementation that keeps the same contract, so it survives refactors.

Read the full file on GitHub · 223 lines

Files

What ships with it

5 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 223 lines · 21 tokens per session scan A df5498dbefbb

Subscribe to this mod's changes

proof is a skill published in the GitHub repository kreek/consult (1 stars, last pushed 7d ago), licensed MIT. It adds 21 tokens to every session and 2,783 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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